The invention relates to the sealing problem in pneumatic, hydraulic and hydropneumatic devices such as gas springs.
For the sealing of an axially movable component, for example a piston rod, it is known to use what are called O-rings. Ordinarily a reception groove is provided to receive the O-ring and the O-ring has a certain play in the axial direction in the reception groove. Accordingly the sealing line on the circumference of the O-ring also rolls on axial movement of the component to be sealed. Especially in those installation cases where the O-ring forms a dynamic seal on the inner diameter and a static seal on the external diameter, for example a dynamic piston rod seal and a static seal against the cylinder inner wall, a relatively great cord thickness of the O-ring is necessary, so that thus high friction and break-away forces are unavoidable in the dynamic seal. By reason of the rolling movement of the O-ring not only does the sealing line roll on the opposed sealing surface, but also a kind of pump effect occurs in which the medium to be sealed is conveyed to the exterior on reversal of direction of movement.
The known sealing rings formed with rectangular or X-shaped cross-sectional area, which abut with two sealing lips on the component to be sealed, also effect a tilting, for example in the axial movement of a piston rod to be sealed, in which the one sealing lip is relieved of load and the other sealing lip is pressed on more strongly. By reason of this tilting movement the danger exists that the medium under pressure may penetrate into the interspace defined by the sealing lips and thus is conveyed to the exterior on reversal of movement.
A sealing packing consisting of a plurality of sealing discs is known from Fed. German Publ. Sp. No. 1,950,381. Such a sealing packing forms a very large sealing area with the piston rod, since each sealing disc abuts on the piston rod over the entire axial thickness. Between the sealing discs support discs are provided which possess a radial play in relation to the dynamic sealing area, whereby the sealing discs are tiltable about the inner edges of the support discs and are pressable on the surface to be sealed with pressure-dependent clamping effect. Such a sealing arrangement possesses an undesirably high friction force between the seal and the movable component to be sealed, as a result of the large sealing area. Furthermore, the break-away forces--stick-slip effect--are very high, so that for example in gas springs or vibration dampers the outward thrust and damping forces are uncontrollably influenced.
It is the object of the present invention to provide a fluid-operated device with a seal which is simple and economical in construction and fitting and guarantees a satisfactory sealing effect without pumping effect with low friction and low break-away forces. This sealing disc should be usable either as a static or as a dynamic seal and, in case of need, be capable of bridging over larger radial distances between two sealing points.